Seal ring

ABSTRACT

A seal ring is provided having rounded lips wherein the top point of sealing is below the top of the ring and the ring has a large area in contact with the sealing surface. The seal ring may have a hollow center portion or a filler strip may be employed in the center of the ring. The filler strip, if used, is of rectangular configuration.

Unite States Patent Felt 1451 Apr. 4, 1972 [54] SEAL RING 343,27710/1921 Germany ..277/205 [72] Inventor: Maurice D. Felt, Carson City,Nev. Primary Examiner Roben L Smith 73] Assignee: Sacomo Sierra Inc.Attorney-Eckhoff and Hoppe 2 F 'l d: l 13 1970 [2 1 y 57 ABSTRACT [2]]Appl. No.: 54,464 1 A seal ring is provided having rounded lips whereinthe top point of sealing is below the top of the ring and the ring has a..277/205, 277/212C large area in Contact with the Sealing surface TheSeal ring 11 may have a hollow center portion or a filler strip may beem- [58] Field of Search "277/161 gs-$5 ployed in the center of thering. The filler strip. if used, is of rectangular configuration.

[56] References Cited 4 Claims, 5 Drawing Figures FOREIGN PATENTS ORAPPLICATIONS 12,424 5/1902 Great Britain ..277/165 PATENTEBAPR 4 I972:Jgl-

MAURICE 0. n

SEAL RING SUMMARY OF THE INVENTION U Ring Type flexible seals are foruse in sealing dynamic and static hydraulic or gas applications forprevention of internal and external leakage. U seals are pressureenergized with pressure against the open end of the U acting equally onthe inner surface in all directions, statically balancing the seal. Useals are normally assembled with an interference fit allowing apositive, relatively low, initial compression. U Ring type seals providegood sealing with low friction at low to moderate pressures, however, aspressure increases frictional wear the the heel or extrusion of the heelare quite likely to be accelerated with subsequent failure of thesealing lips(s).

It is an object of the present invention to provide a configuration thatwill maintain a longer wearing seal at low and accelerated pressureswithout premature failure of the sealing lips and the lips, with theirbulk in the rounded leading edge, will also maintain their seal as thebase or heel of the cup wears or extrudes into the clearance gap betweenthe piston and cylinder wall or the clearance gap between the rod andstuffing box gland. Tests have verified that as the heel wears and/orextrudes the configuration of this invention will cause the upperportion of the sealing lips to lower proportionately as the heelmaterial is lost without failing by tearing, fracturing or flop over,retaining an adequate ability to seal the pressure medium, substantiallyreducing the potential possibility of failure.

The sealing ring of the present invention has a number of advantagesover sealing rings heretofore known. The sealing ring has rounded lipswherein the point of contact between the ring and the wall being sealedis well below the top of the ring. The rounded leading edges are alsohelpful during installation allowing the rings to be installed withoutspecial tools and lessening the possibility of nicking or cutting thelips. This is a design consideration only.

Most of the initial wear on a U cup is on the heel of the cup. As theheel wears it can allow the thinner walls of the lips to fracture orblow by and turn. The heel can also extrude into the clearance gap (whenclearance is excessive or pressures high) between the piston andcylinder wall or rod and stuffing box gland. When this happens the lipcan turn back or fracture. Extrusion or cold flow is minimized in thedesign of the present invention.

The rounded leading edges of the ring of the present invention sealeffectively at low pressures with normal interference. At high pressuresa very effective seal is maintained and with the unique design of thewedge shaped lips the seal can be maintained even with severe wear andextrusion of the heel portion ofthe cup.

Under extremely severe pressures, shock loads, poor surface finishes,etc, the performance can be even further enhanced by adding more bulk tothe heel of the cup, i.e., making the overall height greater than thenominal cross section but leaving the design of the lips the same as inthe standard square cup. This will give more wear surface to the heel,reduce the tendency to extrude and prevent modification of the stressdistribution to the lips of the cup.

U type seals frequently use a filler strip or ring enclosed in theinterior or protruding slightly above the lips of the U. These stripsare normally composed of a material lower in durometer or hardness thanthe material of the seal. This filler strip acts as a spring to furtherincrease the initial contact or interference fit of the lips of the sealat installation and to prevent the bypass of fluid or gas at lowpressures as the cup wears during operation. Some materials used in themanufacture of cups are homogenous in nature without fabricreinforcement and tend to flow or remold under the heat and pressuregenerated during use. Under this condition they do not retain theinterference originally built in and required to maintain a seal atlower pressures. Use of a filler strip is advantageous for thiscondition and the present invention uses a rectangular filler of corkand Buna-N or an elastomeric material such as Buna-N or Neoprene. Thisfiller strip is slightly below the top of the cup lips and is held inplace by the wedge formed by the inward taper of the opposing lips ofthe seal.

In the past, some filler strips have been used in the form of 0 ringsand these tend to be extruded from the cup under certain conditionswhile the ring of the present invention uses a rectangular or wedgeshaped filler strip which locks in place. The rectangular filler stripcauses a very sensitive seal at low pressures or when tolerances areexcessive. The filler strips also prevents the seal from bypassing fluidwhen the cup is overheated in use and then cooled. As the cup wears, thesealing strip also aids in retaining the seal.

Some prior art sealing rings also have required the special provision ofan undercut in the heel to permit stacking when multiple rings areemployed. The design of the present ring is such that a flat heel may beused without interfering with stacking, thus adding to the strength ofthe ring.

Other features of the present invention will be apparent from thebalance of the specification.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of asealing ring embodying the present invention, partly in section.

FIG. 2 is a section of a prior art sealing ring.

FIG. 3 is an enlarged cross section of the sealing ring of FIG. 1.

FIG. 4 is a sectional view showing the sealing ring of the presentinvention in use.

FIG. 5 is a section through a sealing ring of that embodiment of theinvention wherein no filler strip is employed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawingsby reference characters, there is shown in FIG. 1 a packing or sealingring generally designated 6 having a filler strip generally designated8. The sealing ring 6 can be made of any suitable resilient material asis well known to those skilled in the art such as polyester or polyethercastable urethane compounds, preferably having a relatively high Shore Adurometer range, such as to 95. Other elastomeric compounds may be usedsuch as neoprene, natural rubber or a synthetic rubber such as Buna-N.Reinforcing materials such as duck and similar fabrics may or may not beused. One particularly suitable material consists of a polyurethaneresin impregnated with molybdenum disulfide. The filler strip 8 can beeither a compressible material such as cork and Buna-N rubber or arelatively non-compressible material such as neoprene or Buna-N rubber.Obviously many other suitable materials for both the ring proper and thefiller strip will suggest themselves to those skilled in the art.

Describing the ring now in detail, the ring has a base portion 9 andshoulders 11, the base extending generally from the line designated A tothe line designated B and the shoulders extending from line B to line C.Such rings are ordinarily designed for a nominal clearance i.e., theexpected clearance between two parts to be sealed, such as between apiston and a cylinder wall and/or Rod and Stuffing Box, and thisdimension is hereinafter referred to as nominal. In the embodimentillustrated, the distance from A to C, i.e., the overall height of thering was equal to nominal. The top of the shoulder 11 is rounded as at13 and the combined width of the shoulders extends from the line D tothe line E and is slightly larger than nominal, in this case it being1.08 times nominal. The base 9 which extends between the lines F and Gis ordinarily slightly smaller than nominal and in this case was 97percent of the nominal. The shoulders 11 extend upwardly from a root 15and the width of this root is about one-fourth of nominal and the rootdepth is about two-thirds nominal. The inner walls of the shoulders asat 17 taper inwardly slightly, while the outer wall of shoulders 11taper outwardly. Both tapers start substantially from the line B. Theshoulders 11 have top portions 13 and 14 and these are curvedsubstantially through 180 as is shown. The radius of the curve is shownby the arrow H and this radius is about one-fifth nominal.

In the embodiment shown in FIGS. 1 and 3 a filler 8 is provided and thisis in the form of a rectangular insert. As was previously pointed outthe filler can be made from either compressible or non-compressiblematerial and the filler permits more sensitive sealing at low pressureor when tolerances are excessive. The filler also prevents the seal frombypassing fluid when the cup is overheated and then cooled. Since theinner walls of the shoulders taper inwardly, the filler will be graspedand held by the shoulders with the top of the filler somewhatcompressed.

In FIG. 4 the ring is shown in position and in this illustration, it issealing between a stuffing box and a rod 22 and held in place by aretaining ring 24. It will be seen that the initial point of contactbetween the ring 6 and the shaft 22 is far below the top of the ring andis about midway on the shoulder where the curved top portion of theshoulder joins the flat side wall portion. If pressure is increased onsuch a ring, it tends to flatten out, increasing the area of contact ofthe seal, greatly reducing chances of a blowout. Contrast this with theprior art structure shown in FIG. 2. Here it is seen that the initialpoint of scaling is at 26 which is the top point of the shoulder. Aspressure is increased, the ring will flatten against the wall but atstill higher pressures the heel will wear or eXtrude allowing the thinwalls of the lip to fracture or blow by and turn.

Since the O ring which is employed extends above the top of the ring, itis necessary that the base portion be recessed as at 28 to enable aplurality of rings to be stacked. In contrast, the ring of the presentinvention can be used singly or multiply and the base is flat as isshown, giving maximum strength.

In FIG. 5, a modification of the present invention is shown wherein thetiller ring has been eliminated and the base portion, ie. that portionbelow the root of the groove has been greatly enlarged. The root of thegroove is shown at 30 and this leaves a base portion 32 of approximatelytwo-thirds of the overall height of the sealing ring.

Although various embodiments of the invention have been illustrated,wide variations can be made in the exact dimensions shown withoutdeparting from the spirit of this invention. In one embodiment of theinvention, the base was shown to be about onethird of the height of thering while another embodiment was shown to be about two-thirds of theheight of the ring. Obviously, base heights between these extremes canbe employed as well as greater base height, e.g., as much as two timesnominal.

Iclaim:

l. A sealing ring having a cross sectional configuration consisting of agenerally rectangular base and two shoulders extending generallyupwardly from said base, said shoulders having a space between themextending upwardly from a root, the inner surfaces of said shoulderstapering inwardly whereby a filler member may be retained between saidshoulders, the outer surfaces of said shoulders tapering outwardly fromthe level of the root and the upper surfaces of said shoulders beingsymetrically rounded whereby said shoulder will contact a wall beingsealed on said shoulder at a point below the top of said shoulder.

2. The structure of claim 1 wherein the tops of said shoulders arerounded through about 180, the curve having a radius of about one-fifththe thickness of the ring.

3. The structure of claim 1 wherein the base portion of the ring is fromabout A; to of the total height of the ring.

4. The structure of claim 1 wherein a filler member is provided in saidgroove, said filler member being of rectangular cross section and havinga top surface below the top surface of said ring.

1. A sealing ring having a cross sectional configuration consisting of agenerally rectangular base and two shoulders Extending generallyupwardly from said base, said shoulders having a space between themextending upwardly from a root, the inner surfaces of said shoulderstapering inwardly whereby a filler member may be retained between saidshoulders, the outer surfaces of said shoulders tapering outwardly fromthe level of the root and the upper surfaces of said shoulders beingsymetrically rounded 180* whereby said shoulder will contact a wallbeing sealed on said shoulder at a point below the top of said shoulder.2. The structure of claim 1 wherein the tops of said shoulders arerounded through about 180*, the curve having a radius of about one-fifththe thickness of the ring.
 3. The structure of claim 1 wherein the baseportion of the ring is from about 1/3 to 2/3 of the total height of thering.
 4. The structure of claim 1 wherein a filler member is provided insaid groove, said filler member being of rectangular cross section andhaving a top surface below the top surface of said ring.